1. Field of the Invention
The present invention relates to a thermal transfer recording method in which an ink material containing a coloring material comprised of a dye is used for the purpose of recording in such a way that the dye is transferred onto paper or the like by recording means, such as a thermal head.
2. Description of the Prior Art
Hitherto, there has been known a thermal transfer recording method in which recording is effected through the sublimation or diffusion of a dye as a coloring material. According to this known method, an ink sheet comprising a heat resistant base, such as polyethylene terephthalate (PET) film or condenser paper, and an ink material layer of about 3 .mu.m in thickness formed on the surface thereof and comprised of a dye and a binder material is used so that the dye of the ink sheet is transferred directly on a dye-receptive recording medium by a recording head, whereby recording is effected.
The foregoing conventional thermal transfer recording method will be further described with respect to its constitutional aspect and the mode of carrying out the method.
An ink sheet having an ink material layer comprised of a coloring material and a binder material and formed on a heat resistant base, and an image receiving medium, such as recording paper or the like, are pressed in an interface between the thermal head and a platen roller. The thermal head is caused to produce heat in response to a signal from a recording signal source so as to selectively heat up the ink material. Upon separation of the ink sheet from the image receiving medium, a part of the coloring material in the ink material layer is transferred onto the image receiving medium to provide a transferred image.
With the foregoing arrangement, however, the amount of coloring material transfer will vary widely depending upon the type of surface material of the image receiving medium. Since the ink material layer is heated up to cause sublimation or diffusion of the coloring material comprised of a dye for transfer of the coloring material onto the image receiving medium, recording is possible only where the surface material of the image receiving medium is receptive to the dye, and the amount of coloring material transfer depends upon the dye receptivity of surface material of the image receiving medium. For example, where common paper is used as an image receiving medium, image recording through dye transfer can hardly be obtained, because the surface of the paper has little dye receptivity, if any.
Further, with the above described arrangement, the quality of a recorded image varies considerably depending upon the surface condition of the image receiving medium. Any difference in the condition of contact between the image receiving medium and the ink material layer is reflected as a difference in recorded image density and, therefore, the uniformity of the recorded image depends upon the surface smoothness of the image receiving medium. For example, where the image receiving medium has considerable surface irregularity, unsatisfactory contact is unavoidable between the image receiving medium and the ink material layer and, therefore, no uniform image recording can be achieved.